A degradation model of synchronous generator stator insulation

In this work the authors present a degradation model of generator stator insulation to compute failure probabilities. This may in turn be used to develop risk-based maintenance for synchronous generators. First, generators different failure modes were identified and studied. The most common failure mode encountered was failure of the stator winding insulation. Following Simoni´s insulation deterioration model, a mathematical-theoretical insulation degradation model of the stator winding insulation was developed. The model measures degradation in electrical strength through time as a function of generator´s voltage and current. An example for a generator of 13.8 kV and 100 MVA is presented. The results show for the case where the applied voltage and current were at normal operating condition, the winding insulation last approximately three months, while the case at highest applied voltage and highest increase in current, the insulation last a few hours. Complete and reliable data on generators is still needed in order to verify the model and to calculate failure probabilities.